Transport device for photographic development apparatus

ABSTRACT

A transport device for upwardly transporting toner from a holder to an applicator station in an electrophotographic development apparatus. The transport device comprises an endless belt, a lower and an upper roller to determine a path for the belt which extends from the holder to the applicator station. The diameter of the upper roller being smaller than that of the lower roller. The belt is driven at a velocity which is sufficient to remove by inertia and/or centrifugal force at least part of the toner which has been picked-up from the holder and transported by the belt, at the locus where the belt performs a sharp curvature.

Inventor: Karel Frans De Troeyer, B 2000 Antwerpen, Belgium Gevaert-Agfa N.V., Mortsel, Belgi- Filed: Mar. 30, 1971 Appl. N0.: 129,333

Assignee:

Foreign Application Priority Data Mar. 31, 1970 Great Britain ..15,195/70 References Cited United States Patent 1191 1111 De Troeyer 1 1 May 8, 1973 1541 TRANSPORT DEVICE FOR 3,601,091 11 1971 Preekshot .1111 030 PHOTOGRAPHKI DEVELOPMENT Z132; mt;

, a v. APPARATUS 3,133,833 5/1964 Giaimo, Jr ..1 18/637 Primary Examiner--Mervin Stein Assistant Examiner-Leo Millstein AttorneyWilliam J. Daniel [57] ABSTRACT A transport device for upwardly transporting toner from a holder to an applicator station in an electrophotographic development apparatus. The transport device comprises an endless belt, a lower and an upper roller to determine a path for the belt which extends trom the holder to the applicator station. The diameter of the upper roller being smaller than that of the lower roller. The belt is driven at a velocity which is sufficient to remove by inertia and/or centrifugal force at least part of the toner which has been pickedup from the holder and transported by the belt, at the locus where the belt performs a sharp curvature.

13 Claims, 5 Drawing Figures PATENTEDW 81913 3,731,656

SHEEI 2 [IF 3 TRANSPORT DEVICE FOR PHOTOGRAPHIC DEVELOPMENT APPARATUS The invention relates to a photographic development apparatus comprising transport means for upwardly transporting a developer composition from a supply station. More particularly the invention relates to an electrophotographic development apparatus wherein a support carrying an electrostatic charge pattern is developed by means of an electrostatically attractable toner which is uniformly distributed over the support carrying the charge pattern.

Within the terms of the present application the expression developer composition points both to developers in finely divided solid state as used in electrostatic printing apparatus and to developers in liquid state, e.g. developers wherein pigment particles are suspended in a liquid phase with a very high specific resistance.

It is known to apply toner onto a charge pattern carrier by means of a roller partly immersed in a body of toner contained in a holder and pressing against the higher located moving charge pattern carrier. in this way only a limited difference in height can be bridged and the direct contact between the applicator roller and the charge pattern carrier may be an undesirable phenomenon in many cases.

It is also known to use a so-called dredging device for upwardly transporting the developer composition from the holder. Such transport means is a very complicated and quite voluminous mechanism wherein moreover the developer composition is fed in a discontinuous way. The latter drawback may give rise to faults in the developed image.

It is an object of the present invention to provide an apparatus which does not show the mentioned drawbacks and wherein the favorable influence on the photographic quality of a high turbulence during the developing stage can be exerted.

It is a further object of the invention to form an aerosol without causing turbulence in the surrounding gas and to form an aerosol even in vacuum.

According to the present invention a transport device for transporting developer composition from a holder or collector containing such composition towards a higher located applicator station, comprises (a) an endless belt,

(b) means which determines for said endless belt a path which extends from said holder to said applicator station and which has a sharp curvature near the said applicator station, and

(c) means for rotating said belt at a velocity which is sufficient to remove by inertia and/or centrifugal force at least part of the developer composition which has been picked up from the holder and transported thereby, at the locus where the belt performs a sharp curvature.

The present invention is described more in detail by way of the following embodiments with reference to the accompanying drawings, in which FIG. 1 is a diagram of the transport device according to the invention,

FIG. 2 shows a detail of a modified embodiment of the invention,

FIG. 3 shows an other embodiment of the invention,

FIGS. 4 and 5 are further embodiments of the inventron.

The apparatus illustrated in FIG. 1 is a conventional xerographic printing apparatus. The original to be reproduced is placed on a support tray 10 from which it is fed to a transport arrangement designated 1 1. On the transport arrangement the original is moved on an endless belt 12, driven by a motor 13 to pass the optical axis of projection system 14 that is illuminated by projection lamp 1. The image of the original is reflected by a mirror 15 through an adjustable objective lens 16 and then reflected by mirror 17 downwardly through a variable slit aperture assembly 18 and onto the surface of a xerographic plate in the form of drum 19.

Xerographic drum 19 includes a cylindrical member mounted in suitable bearings in the frame of the machine and is driven in a clock-wise direction by a motor 24 at a constant rate that is proportional to the transport rate of the original, whereby the peripheral rate of the drum surface is identical to the rate of movement of the projected radiation image. The drum comprises a layer of photoconductive material in a conductive backing that is sensitized prior to exposure by means of corona generating device 25 that is energized from a suitable high potential source.

Exposure of the drum surface to the radiation image discharges the photoconductive layer in the area struck by radiation whereby there remains on the drum a latent electrostatic image in image configuration corresponding to the radiation image projected from the original.

As the drum continues its movement the latent electrostatic image passes through developing station 26 where the latent image is developed in accordance with the invention as will be described below.

After development the toner image passes a discharge station 50 at which the drum surface is illuminated by lamp 2 whereby residual images on the nonimage areas of the drum surface are completely discharged.

Thereafter, the toner image passes through an image transfer station 51 at which the toner image is electrostatically transferred to a moving support surface 52 by means ofa second corona generating device 53 similar to corona charging device 25, mentioned above.

The moving support surface 52 to which the toner image is transferred may be of any convenient type, such as paper, and may be obtained from a supply roll 56, fed over guide roller 57 and over suitable tensioning rollers being directed into surface contact with the drum in the immediate vicinity of transfer corona generating device 53. After transfer, the support surface 52 is separated from the drum surface and guided through a fusing apparatus 58 wherein the toner image is permanently affixed thereto. The toner image may be fixed e.g. by means of a laser beam. Thereafter, the support surface may be fed over a further system of guide and tensioning rollers, and onto a take-up roller 60 that is driven through suitable drive means by motor 61.

After separation of the support surface 52 from the drum, a corona generating device 64 directs electrostatic charge to the residual power image on the drum surface. Thereafter, the xerographic drum surface passes through a cleaning station 65 where its surface is brushed by a cleaning brush assembly 66, rotated by a motor 67, whereby residual developing material remaining on the drum surface is removed. The drum surface then passes through a second discharge station 68 at which it is illuminated by a fluorescent lamp 3, whereby the drum surface in this region is completely flooded with light to remove any electrostatic charge that may remain thereon. Suitable light traps are provided in the system to prevent any light rays from reaching the drum surface, other than the projected image during the period of drum travel immediately prior to sensitization by corona generating device until the drum surface is completely passed through the developing station 26.

Referring now to the development apparatus as illustrated in FIG. I, the apparatus comprises an endless powder bearing donor belt 27 which is tensioned over the rollers and 31 and which is advanced in the direction of the arrow at a linear velocity of about 1100 cm/s by means of a motor 33 driving the lower roller 31. The roller 30 has a diameter of about 5 mm and is situated near the drum 19. The belt 27 may be electrically conductive or insulating and may consist of any material flexible and durable enough to be formed in an endless belt. The belt may comprise such materials as metal sheets, conductive rubbers, fabric, paper, Mylar (a durable film of polyethylene terephthalate resin), or the like, governed by such other factors such as cost, availability, useful life, etc.

The belt 27 is initially loaded with a thin uniformly distributed, releasable layer of toner particles 36. Loading can be effected by leading the belt 27 through holder 44 comprising the toner particles 36.

The toner particles adhere to the outer surface of the belt and they are carried upwardly as the belt rotates. Near the end of the upward movement, the course of the belt is abruptly deviated as the belt passes around the small roller 30 so that due to insertion, at least part of the quantity of toner which is carried upwardly leaves the belt and continues its rectilinear path. Alternatively or in addition, at least some of the toner may be made to remain on the belt when it starts to pass around the small roller 30 so that such toner becomes flung off the belt by the strong centrifugal forces. The toner particles strike the drum I9 uniformly and they remain attracted to the drum surface in accordance with the electrostatic charge pattern on the drum. The surplus quantum of the toner particles slides downwardly over the drum and is recollected into the holder 44 where the rotational movement of the roller 31 and the belt 27 ensure a uniform distribution of the particles in the holder.

The rate at which toner is flung off onto the drum 119 can be influenced by the type, the form and the running speed of the belt 27, the diameter of the roller 30, the distance between the drum l9 and the roller 30, by the properties of the toner and occasionally by the application of an adjustable voltage difference between the drum l9 and the roller 30.

The adhesion of the toner powder to the belt can be improved by roughening the top surface of the belt or by providing said surface with transverse ribs. The feeding of toner powder carried upwardly can be dosed by arranging a scraper at an area between rollers 30 and 31 above the path of the belt. Moreover, the supply oftoner powder can proceed very uniformly thereby.

For further improving the adhesion of the toner powder advantage is taken of the fact that the toner powder can be charged electrically and is attracted in said condition by charges of opposite polarity. For instance the roller 31 may be biased with such a voltage that the toner particles are attracted onto the belt whereas the roller 30 is connected to an opposite voltage so that the toner powder may be released from the belt. In a like manner a voltage difference may be applied between the drum 19 and the roller 30 whereby the travel speed of the powder to the drum 19 is accelerated.

According to a further embodiment of the invention, illustrated in FIG. 2, there is provided an applicator roller 32 in direct contact with the drum 19. Preferably the surface of the applicator roller 32 is coated with a layer of elastomeric material, e.g. with a 3 mm thick layer of flexible polyurethane foam on a support such as aluminum. The applicator roller 32 rotates at a peripheral speed slightly higher or lower than the peripheral speed of the rotating drum 19 so as to produce a relative surface motion therebetween effective to uniformly distribute the powder on the drum surface. When electrically conductive, the roller 32 can conveniently be biased to a voltage of a polarity opposite to that of the toner particles in order to suppress background charge and to prevent its development.

The drawing according to FIG. 3 shows a detail of an embodiment wherein the developer is flung off against a reversing plate 35 and is falling down in a space between this reversing plate 35 and a protecting plate 37 from where the toner powder is applied to the drum 19.

In a further embodiment of the invention, illustrated in FIG. 4 the belt is guided over three rollers 30, 31 and 34 wherein the rollers 31 and 34 are positioned at the same height.

According to another embodiment of the invention, illustrated in FIG. 5 the belt 27 is composed of a rela tively thick resilient material such as butyl rubber, provided at its outer surface with cavities 45 the opening of which is narrower than the greatest width thereof. At the area where the belt passes on the roller 30 and is strongly curved, the opening of the cavities 45 is widened so that e.g. the developer is made to escape by centrifugal force from the opened cavities 45. In this way, an accurate dosing of the amount of flung off developer is made possible. Besides, the foregoing em bodiment can be used for the application of powder which otherwise could not be picked up easily by the belt. In this embodiment of the invention rollers 30 and 3ll must have a relatively small diameter.

In an alternative embodiment of the invention the belt 27 consists of a plurality of jextaposed endless strings.

The direction in which the developer is flung off may be influenced by changing the sense of rotation of the belt. The distribution of the flung off developer may be influenced by an adjustable guide plate 46 provided with a slit aperture 47 arranged between drum l9 and roller 32 or 30 as indicated diagrammatically in FIG. 5.

Although the invention has been described with reference to the details and construction herein illustrated, it is not intended to be confined to the exact mechanism shown. Use can also be made of the described devices for other purposes than the application of photographic developer, e.g. for the dosed feed ing of toner powder in a replenishing unit for the application of paint coatings on walls.

We claim 1. Apparatus for contacting fluent developer com position with a developable photographic material comprising:

l. means for advancing said photographic material along a fixed path,

2. an endless conveyor belt having a generally straight stretch extending toward said fixed path and terminating in spaced proximate relation to said material path in a reversely curved portion with a small radius of curvation,

3. means for applying said fluent developer composition to successive regions of said belt at a locus remote from said reversely curved portion, and

. means for driving said endless belt at a high velocity sufficient to project said fluent composition from said belt by centrifugal force when said successive belt regions move along said reversely bent portion, said composition being projected in a direction intersecting at an angle with said material path to impinge against the material advancing through said path, said fluent composition being in free floating condition between the point of departure from said belt and the point of impingement with said material.

2. Apparatus as in claim 1 wherein said belt passes through a body of said fluent developer composition which adheres to said belt.

3. Apparatus according to claim 2 wherein the outer surface of the endless belt has been roughened to increase the adherence of the developer composition thereto.

4. Apparatus as in claim 1 wherein said generally straight stretch of said endless belt is inclined upwardly toward said reversely curved portion.

5. Apparatus as in claim 1 including at least one roller.

6. Apparatus as in claim 1 wherein said endless belt is provided with superficial recesses over substantially the entirety of the external surface thereof to receive said developer composition.

7. Apparatus as in claim 6 wherein said recesses are in the form of successive closely spaced transverse grooves.

8. Apparatus as in claim 1 including an apertured along a fixed path,

an endless conveyor belt having a generally straight stretch extending toward said fixed path and terminating in spaced proximate relation to said material path in a reversely c'urved portion with a small radius of curvation,

3. means for applying said fluent developer composition to successive regions of said belt at a locus remote from said reversely curved portion,

. an applicator roller arranged for peripheral contact with the photographic material advancing along said fixed path generally between said reversely curved belt portion and said path, and

5. means for driving said endless belt at a high velocity sufficient to project said fluent composition from said belt by centrifugal force when said successive belt regions move along said reversely bent portion, said composition being projected in a direction to impinge against the applicator roller periphery, said fluent composition being in free floating condition between the point of departure from said belt and the point of impingement with said roller periphery, said roller spreading the composition impinged thereon over the photographic material.

12. Apparatus as in claim 11 wherein said applicator roller has a peripheral layer of elastomeric material.

13. Apparatus as in claim 11 wherein said applicator roller is rotated at a peripheral speed different from the speed of advance of the photographic material along its fixed path. 

1. Apparatus for contacting fluent developer composition with a developable photographic material comprising:
 1. means for advancing said photographic material along a fixed path,
 2. an endless conveyor belt having a generally straight stretch extending toward said fixed path and terminating in spaced proximate relation to said material path in a reversely curved portion with a small radius of curvation,
 3. means for applying said fluent developer composition to successive regions of said belt at a locus remote from said reversely curved portion, and
 4. means for driving said endless belt at a high velocity sufficient to project said fluent composition from said belt by centrifugal force when said successive belt regions move along said reversely bent portion, said composition being projected in a direction intersecting at an angle with said material path to impinge against the material advancing through said path, said fluent composition being in free floating condition between the point of departure from said belt and the point of impingement with said material.
 2. an endless conveyor belt having a generally straight stretch extending toward said fixed path and terminating in spaced proximate relation to said material path in a reversely curved portion with a small radius of curvation,
 2. an endless conveyor belt having a generally straight stretch extending toward said fixed path and terminating in spaced proximate relation to said material path in a reversely curved portion with a small radius of curvation,
 2. Apparatus as in claim 1 wherein said belt passes through a body of said fluent developer composition which adheres to said belt.
 3. Apparatus according to claim 2 wherein the outer surface of the endless belt has been roughened to increase the adherence of the developer composition thereto.
 3. means for applying said fluent developer composition to successive regions of said belt at a locus remote from said reversely curved portion,
 3. means for applying said fluent developer composition to successive regions of said belt at a locus remote from said reversely curved portion, and
 4. means for driving said endless belt at a high velocity sufficient to project said fluent composition from said belt by centrifugal force when said successive belt regions move along said reversely bent portion, said composition being projected in a direction intersecting at an angle with said material path to impinge against the material advancing through said path, said fluent composition being in free floating condition between the point of departure from said belt and the point of impingement with said material.
 4. an applicator roller arranged for peripheral contact with the photographic material advancing along said fixed path generally between said reversely curved belt portion and said path, and
 4. Apparatus as in claim 1 wherein said generally straight stretch of said endless belt is inclined upwardly toward said reversely curved portion.
 5. Apparatus as in claim 1 including at least one roller.
 5. means for driving said endless belt at a high velocity sufficient to project said fluent composition from said belt by centrifugal force when said successive belt regions move along said reversely bent portion, said composition being projected in a direction to impinge against the applicator roller periphery, said fluent composition being in free floating condition between the point of departure from said belt and the point of impingement with said roller periphery, said roller spreading the composition impinged thereon over the photographic material.
 6. Apparatus as in claim 1 wherein said endless belt is provided with superficial recesses over substantially the entirety of the external surface thereof to receive said developer composition.
 7. Apparatus as in claim 6 wherein said recesses are in the form of successive closely spaced transverse grooves.
 8. Apparatus as in claim 1 including an apertured shield interposed between said reversely curved belt portion and said material path to control the distribution of the projected developer composition on said material.
 9. Apparatus according to claim 1 wherein said radius curvature is smaller than about 2.5 mm.
 10. Apparatus according to claim 1 wherein said developer composition is in the form of finely divided electrostatically attractable particles, and said photographic material is a xerographic element carrying an electrostatic image charge pattern.
 11. Apparatus for contacting fluent developer composition with a developable photographic material comprising:
 12. Apparatus as in claim 11 wherein said applicator roller has a peripheral layer of elastomeric material.
 13. Apparatus as in claim 11 wherein said applicator roller is rotated at a peripheral speed different from the speed of advance of the photographic material along its fixed path. 